Attitude control of fly wing UAV with multi-boundary state constraints

To solve the flight attitude control problem under multi-boundary state constraints and strong disturbance, a joint command-control law limiting full state constraint control approach is proposed, with a high-aspect-ratio flying wing UAV as the research model. This control approach consists of three independent parts: command limiter, reference generator and command tracker. Firstly, based on the aircraft dynamic characteristics, the command limiter utilizes each state bound to restrict attitude command. In this way, the constraint problem of non-controlled states is converted into a constraint problem of controlled states. Secondly, the reference generator provided a command trajectory from the current attitude to the desired attitude. This online process is achieved according to the idea of “transition process arranging” and considering the constraints. Finally, the command tracker is designed based on barrier Lyapunov function and extended state observer, which enable the UAV overcoming disturbance and tracking command trajectory quickly and stably. The stability is analyzed by means of Lyapunov theory. Attitude tracking error is proved to be bounded-convergent and always remain in the given region. Simulation results show that UAV tracks the desired attitude command accurately. Moreover, the established controller can prevent flight states from exceeding limitation.